Method of making open-hearth steel.



NITED STATES Patented June 20, 1905.

PATENT OFFICE.

METHOD OF MAKING OPEN-HEARTH STEEL.

SPECIFICATION forming part of Letters Patent No. 792,914, dated June 20, 1905.

Application filed April 5, 1902. Serial No. 101,591.

To all whom it 117/04, concern:

Be it known that I, NIVEN McOoNNnLL, of Pittsburg, Allegheny county, Pennsylvania, have invented a new and useful Method of Making Open-Hearth Steel, of which the following is a full, clear, and exact description.

My invention reduces greatly the time heretofore necessary in making open-hearth steel, and thereby increases the output'and reduces the expense.

In carrying out my invention I introduce molten pig metal into an acid-lined converter, which may be of ordinary type, and blow air through it in the manner common in Bessemer practice until the silicon has been removed, the carbonconsiderably reduced, and the temperature of the metal raised by the reaction to a point corresponding with that required for keeping it melted notwithstanding its loss of carbon. I prefer to reduce the carbon content of the metal to about one per cent, although this percentage may be varied within considerable limits; but as the converter is acid-lined the phosphorus is not substantially removed from the metal. When the carbon has reached the desired point, the desiliconized and partially-decarburized metal, which is then in the condition of semisteel, is transferred from the converter into an intermediate regenerative furnace, in which a large body of such metal is held under the influence of heat. The final treatment of the metal is effected in basic lined open-hearth furnaces, into which charges of the molten metal are transferred from the intermediate furnace as they are required. For illustration, the in termediate furnace may hold from two hundred to three hundred tons of the desiliconized and partially-decarburized metal, and the basic open-hearth furnaces in which it is finally treated may have a capacity of fifty tons. In the open-hearth furnaces the metal is treated with basic additions in the usual manner, the phosphorus is eliminated, the carbon reduced to the desired point, and the temperature of the metal is raised to the degree required for casting.

The operation which I have described is a continuous operation in that the metal is charged into the intermediate furnace as soon as it is taken from the converters, and a large store of the metal being kept on hand therein the final furnaces can be supplied with metal whenever they are ready, so that there is no delay at any stage of the operation. More over, in the intermediate furnace the composition of the metal is equalized by mixing and its temperature is equalized by the heat of the gases, so that charges of standard and uniform character can be supplied to the final furnaces.

The operations of the plant are easily controllable, and the process enables me to dispense with scrap, for the metal is rapidly desiliconized and partially decarburized before it is delivered to the open-hearth furnace, and the final operation to which it is subjected therein is short, so that the whole process can be completed in a much shorter time than when it is attempted to make steel directly in an open-hearth furnace without the aid of scrap.

I claim- 1. The method herein described of making steel which consists in blowing pig metal in converters, desiliconizing and partially decarburizing it therein, transferring the desiliconized and partially-decarburized metal from the converters to an intermediate furnace from time to time as it is supplied by the converters, maintaining and heating in the intermediate furnace a large body of such metal, transferring from time to time charges of such metal to basic open-hearth furnaces, and dephosphorizing and decarburizing it therein; substantially as described.

2. The method of making steel, which consists in blowing pig metal in a plurality of converters, desiliconizing and partially decarburizing it therein, transferring the desiliconized and partially-decarburized metal from the several converters to a common intermediate furnace from time to time as it is supplied by the converters, maintaining in the intermediate furnace a large body of such metal, applying external heat to the molten bath of metal, transferring from time to time charges of such metal to basic open-hearth furnaces, and dephosphorizing and decarburizing it therein; substantially as described. I

3. The method of making steel, consisting in blowing pig metal in a pool in a converter, thereby clesiliconizing and partially decarbu rizing it therein, and at the same time increasing its temperature, transferring the hot metal thus obtained to an intermediate furnace from time to time, maintaining a large pool in the intermediate furnace, applying external heat to the said pool, and transferring charges forming a portion of the metal of such pool from time to time to basic open-hearth furnaces and dephosphorizing and decarburizing it therein; substantially as described.

4. The method of making steel consisting in blowing a pool of molten pig metal in an acid-lined converter, desiliconizing and partially decarburizing it therein and at the same time increasing its temperature, transferring the hot metal thus obtained to an intermediate furnace from time to time, maintaining a large pool in the intermediate furnace, applying external heat to the said pool, and transferring charges forming a portion of the metal of such pool from time to time to basic openhearth furnaces and dephosphorizing and deoarburizing it therein; substantially as described.

In testimony whereof I have hereunto set my hand.

NIVEN MOCONNELL. l/Vitnesses:

G. B. BLEMING, H. M. CORWIN. 

